package com.lagou.sqlSession;

import com.lagou.pojo.Configuration;
import com.lagou.pojo.MappedStatement;
import com.lagou.utils.TransLateHander;

import java.lang.reflect.*;
import java.util.List;

public class DefaultSqlSession implements SqlSession {

    private Configuration configuration;

    public DefaultSqlSession(Configuration configuration) {
        this.configuration = configuration;
    }

    @Override
    public <E> List<E> selectList(String statementid, Object... params) throws Exception {

        //将要去完成对simpleExecutor里的query方法的调用
        simpleExecutor simpleExecutor = new simpleExecutor();
        MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementid);
        List<Object> list = simpleExecutor.query(configuration, mappedStatement, params);

        return (List<E>) list;
    }

    @Override
    public <T> T selectOne(String statementid, Object... params) throws Exception {
        List<Object> objects = selectList(statementid, params);
        if(objects.size()==1){
            return (T) objects.get(0);
        }else {
            throw new RuntimeException("查询结果为空或者返回结果过多");
        }
    }

    public int update(String statementid, Object... params) throws Exception {
        //将要去完成对simpleExecutor里的query方法的调用
        simpleExecutor simpleExecutor = new simpleExecutor();
        MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementid);
        Object object = simpleExecutor.update(configuration, mappedStatement, params);
        return (int)object;
    }

    @Override
    public <T> T getMapper(Class<?> mapperClass) {
        // 使用JDK动态代理来为Dao接口生成代理对象，并返回

        Object proxyInstance = Proxy.newProxyInstance(DefaultSqlSession.class.getClassLoader(), new Class[]{mapperClass}, new InvocationHandler() {
            @Override
            public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
                // 底层都还是去执行JDBC代码 //根据不同情况，来调用selctList或者selectOne
                // 准备参数 1：statmentid :sql语句的唯一标识：namespace.id= 接口全限定名.方法名
                // 方法名：findAll
                String methodName = method.getName();
                String className = method.getDeclaringClass().getName();
                String statementId = className+"."+methodName;
                // 获取statementId对应的sql语句
                MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementId);
                // 将sql语句与params交于executor进行处理
                final simpleExecutor simpleExecutor = null;
                return execute(method,mappedStatement.getSql(), args);


            }
        });

        return (T) proxyInstance;
    }

    public Object execute(Method method,String sql, Object[] args) throws Exception {
        // 底层都还是去执行JDBC代码 //根据不同情况，来调用selctList或者selectOne
        // 准备参数 1：statmentid :sql语句的唯一标识：namespace.id= 接口全限定名.方法名
        String methodName = method.getName();
        String className = method.getDeclaringClass().getName();
        String statementId = className+"."+methodName;
        //截取6位sql 并将截取sqlType转换大写
        String sqlType = TransLateHander.getCommodType(sql);
        //判断mapper中的方法类型，最终调用的还是SqlSession中的方法
        switch (sqlType) {
            case "INSERT": {
                System.out.println("insert方法");
                return update(statementId, args);
            }
            case "UPDATE": {
                 System.out.println("UPDATE方法");
                 return update(statementId, args);
            }
            case "DELETE": {
                System.out.println("DELETE方法");
                return update(statementId, args);
            }
            case "SELECT":{
                // 准备参数2：params:args
                // 获取被调用方法的返回值类型
                Type genericReturnType = method.getGenericReturnType();
                if(genericReturnType instanceof ParameterizedType){
                    List<Object> objects = selectList(statementId, args);
                    return objects;
                }
                System.out.println("select方法");
                return selectOne(statementId,args);
            }
            default:
                throw new Exception("sql错误！");
        }
    }

}
